Irregular Shoulder

Question
Hello,
I recently noticed an irregularity on my horse's right shoulder blade.  The scapula on this side seems to have an odd protuberance of about 3 inches by less than one inch along the slope of the shoulder.  I am really not sure how long this has been this way, I've noticed it before but thought it was just from the way my horse was standing. I recently investigated more closely and there is definitely a difference from his left shoulder.   There is no pain associated with the area, I can poke and prod at it with no response.  My horse moves freely and without any sign of lameness, in fact, his right side is his "better" side.
    The horse is seven years old.  I have worked with him since he was a yearling and he has never had any history of lameness or other health problems.  I am not sure how long this irregularity has been there, as it is something I only recently took notice of but could have been there for awhile.
My question is whether or not this is likely just a harmless abnormality that I can mention to the vet when vaccination time comes around or if it sounds like something I should investigate more aggressively.

Thank you for your time!

Answer
Im not sure that I can visualize what you are describing. I believe this is probably not of any clinical significance, but you should have someone look at it to determine if that is the case. One thought that at least crrosses my mind is that you may be seeing this due to loss of muscle in that area. The "protuberance" may then be actually normal bone structure that becomes obvious when the muscle that normaally overlies is reduced or lost. Horses can develop muscle loss of the shoulder with increased visibility of the spine of the scapula (a portion of the scapular bone) when there is an injury to the suprascapular nerve. this condiditon is also referrred to as "sweeney". If this occurs, when the horse walks, if you watch him from in front, the affected shoulder rolls out (rotates outward) when weight is placed on that limb. Im not sure that thats what you are describing, it really needs to be seen to determine if thats the case. I really dont think that it is a major concern though. Let me know what you find out. Good luck.